Electric fuse



(NowModel.)

. K. J. SUNDSTRM.

ELECTRIC FUSE.

No. 374,640. Patented Dec.v13, 1887.

e. i n .m lm F IN'VENTOR Z unimi/1mm,

WITNESSS Unirse S'rmrss KARL JOHN SUNDSTRM, OF DOVER, NEW JERSEY, ASSIGNOR OF ONE- l HALF IO JAMES MACBETH, OF BROOKLYN, NEW YORK. Y

ELECTRIC FUSE.,

SPECIFICATION forming part of Letters Patent No. 374.640, dated December 13, 1887.

Application filed July i3, 1887.

To all whom it may concern.-

Beit known that LKARL JOHN SUNDs'rRM, residing at Dover, in the county of Morris and State of N ew Jersey,haveinvented certain new and useful Improvements in Electric Fuses, of which the following is a specification.

Electric fuses or exploders for exploding blasting charges and the like have heretofore been constructed with a iine platinum wire as the incandescent conductor, by the heating of which upon the passage of the electric current the explosive charge is ignited. The platinum wire has been connected to the leadingin or conducting wires by soldering-a process which is very difficult to perform, and which renders such fuses expensive of construction.; There is also liability that in the putting together of the parts constituting the fuse the delicate platinum wire will be broken or become disconnected, therebyrenderingthe fuse inoperative. Defects of this character are undiscoverable,except bythe failure of the charge to explode-an occurrence which results frequently in great loss and inconvenience.

My invention aims to produce au electric exploder which shall be free from the disadvantages incident to the employment of platinum Wire as the incandescent conductor-` To this end I employ the usual insulated leady ing-in wires and at some convenient point I remove the insulation and insert the wires into the shell of the exploder, with the portions thus bared of insulation in contactl with pow dered carbon or other comminuted conducting material of sufciently high resistance to become incandescent upon the passage-of an. electric current of the character ordinarily employed for igniting blasting charges. The conducting-wires maybe looped or not, their bared portions in either case being preferably at the extremity. The insulation is prefera bly removed by cutting an angular notchbetween the extremities of the wires or loops of wire,so that upon dipping or pressing the wires into a mass of powdered carbon enough of the latter will be pressed into the notch to remain there and constitute the inandescing conductor.

Figure l of the accompanying drawings is SerialNo. 245.087. (No model.)

a longitudinal mid-section of an electric fuse or exploder constructed according to my invention in its preferred form. Fig. 2 is a transverse section thereof cut on the line 2 2 therein. Fig. 3 is a fragmentary view, on an enlarged scale, of the electric ductors removed from the shell'. Fig. 4 is a similar view looking in a vdirection at right angles to Fig. 3. In both these views the wires are partly broken away orin section to show the construction. Fig. 5 `is a similar View illustrating a modified construction of primer. Fig. 6 is an oblique elevation of a further modiiication. Fig.- 7 is a longitudinal midsectiou of the fuse, showing another modification.

Referring to Fig. l1, let A designate the .usual metallic shell' of the fuse or exploder,

which contains the u'sual charge of fulmmate,

and in which is placed the electric primer B. This primer consists of two leading-in wires, b b, which are connect-ed together by being` twisted or otherwise, and are, as usual, inclosed in insulation. According to the Vpreferred construction, which is shown in Figs. 1 to 4,

their ends are doubled back upon themselves,

primer or con- .T5 and the doubled end portions of thetwozwires.

are bound firmly together by a sheath, C, consisting of a wrapping of thread, wire', orI any other .suitable material. The .doubled or looped `what beyond this sheathy and lie parallel to each other and in close contact, the conducting-wires being separated from one another only by their insulatingcovering. After the wires are connected in this manner, the insulation is removed from the extremity of their looped portions Aby. means of a three sided ile, or by a suitable grinding-wheel, or in any other convenient manner, by which, preferably, an angularorV-shaped notch is cut through the insulation and partially into the metallic wires, as clearly show'n in Fig. 3. In this manner a surface of the metallic wires is exposed at au, which should be, by preference, of somewhat greater area than that of the crosssection of the wires. It is obvious that if wires thus prepared be dipped intofa mass of powdered carbon and an electric current of sufficient energybe, sent through the wires, enterends of the two wires projectsomef' 65 E,of wood or other suitable material, and

carbon and passing'out by the other wire, the particles of carbon will be heated to incandesccnce in the path of the elect-ric current. I avail myselfy of this fact in the construction of my electric fuse. l

Before placing the primer 'in the shell I thrust its end,where the notch has beenformed through the insulation, into a mass of inelypowdered retort carbon, pressing it into the mass, and thereby forcing the carbon into the notch vand into close contact with the bared portions a a of the wire. Upon removing the primer a small mass of carbon remains firmly compacted into the notch, as shown at D in Fig. 3, and this constitutes the incandescing conductor of the primer. The primer is then inserted into they shell A, inwhich has previously been placed the customary charge of fulmiuate. The primer is placed with its carbon D against .the top of the fulminate, and then, by preference, a small quantity of fulminate is filled in around the terminals of the, primer, or some gunpowder or gun-cotton may be inserted. Finally, the usual ii-lling, F, of sulphur or other suitable cement or plastic material, is run into the ppper portion of the shell around the primer, in order to hold the latter 1n place and to hermetically close the explo'der and exclude moisture therefrom.

The precise construction of shell A audits contents, .which I have herein shown and described, is not essential to my invention; butany construction or arrangement of the parts or elements of .the exploder other than those to which my invention specially pertains may be employed. For example, the shell A may be of various shapes and may be closed or sealed in various ways-such, for example,'a's in any ofthe constructions of electric expl'oders heretofore made. Any explosive material- .may be used,and the powdered carbon or otherl comminuted conducting substance may b'e ar'- Aranged in any suitable way relatively to the explosive, as may be preferred inany particular instance.

The primerB may be heldv in place Within the 'shell by any of the means heretofore employed for fastening leading-in wi res, and may itself be constructed in various ways, :of which some examples, in addition to the preferred method already described, are shown in Figs. 5, 6, and 7 of the drawings.

Fig.5 shows the two conducti ng`wiresjoine`d together by a sheath, 0, substantially as'al' ready described, but without having their'end portions doubled back upon themselves.v The extreme ends ofthe wires lie side by side, separated only by their insulation, and between them an angular notch is formed by means of a. [ile or otherwise, as already described, thereby preparing the ends of the wires for making contact with the powdered carbon.

Fig. 6 shows a construction wherein the sheathC is omitted, the end portions of the wires B B being looped around a small bar,

twisted together above the same, or otherwise firmly joined o'r bound together. -An angular notch is filed in the looped portions of the wires beneath the bar E, as shown, to remove the insulation and expose a bright or untarnished surface of the conducting-wires. When placed in the shell A, the ends of t-he bar E may be made to tit against the sides thereof,

and therebyrhold the conductors in the proper position within the shell while the filling of sulphur or other scaling substance is being run in.

Fig. 7 shows the two conducting-wires b b I primer before the latterisinserted in the shell,

but is first placed in the shell, lying in a hollow formed to receive it in the top of the mass of fulminate, so that when the primer is inserted its terminals are thrust or embedded into the loose powder, after which the filling of sulphur, resin, or other substance, F, is run in. l

Instead of employing powdered carbon for t the incandescing conductor, the terminals of the electric conductors may be thrust into a mass of loose gunpowder, which will itself serve'as 'a high-resistance conductormalthough not so suitable for the purpose as the carbon, since it contains a less proportion of conducting substance. AThe carbon, instead of being in the form o'f a powder, may be in the conv dition of a 4plastic paste, which may harden aro'und the conductors after the latter are thrust into it. Thus my invention is not limited absolutely to the employment of the incandescing conductor in a comminuted condition. It is, however, essential to my invention ythat the incandescing conductor shall be in such condition that when the bared termi,

n'alsof the conducting-wires are thrustinto it itvshall make an electric connection with said terminals, thereby avoiding all soldering or other joining or connecting of the incandescin'g. with the leading-in conductors before their insertion into the shell.

The particulary construction by which this desideratum4 is' realized may be varied considerably within the limits of .my invention.

The sheath C, although consisting, preferably, o'f a wrapping of soft thread or tine wire,

may be made of a sleeve or band of leather, rubber', cotton, or other textile material, or of copper, lead, or other metal, inte which the wires may be thrust, or which may be wrapped or closed around the wires, as may be preferred.

My improved electric fuse presents the advantages of cheapness of manufacturefsimplicity of construction, reliability-there being nothing that can break or get out of order Vand thereby destroy or impair the electrical connections-of being safer to make and hanadjacent portions bared of insulation with au l sulated conductingwires having relativelyand with an -incandescing conductor consist' incandescing conductor consisting of a mass of carbon lying between the bared portions of the wires.

2. In an electric fuse, the combination of insulated conducting-wires having their terminal portions doubled'upon themselves and having adjacent portions upon the loops thus formed bared of insulation with'an incandescing conducto-r consisting of a mass of matey rial of high electric resistance lying between thebared portions of the wires.

3. In an electric fuse, the combination of inadjacent portions -bared of insulation with a sheath by which said Wires are bound together,

ing of a mass of comminuted material of high electric resistance lying between the bared port-ions of the wires.

portions bared of insulation, a sheath, C,-bind ing said wires together, an ,incandescing conductor consisting of a mass of comminuted material of high electric resistance lying between-the bared portions of said wires", and a filling of plastic material placed around said 'conductors and sealing said shell.

5. A primer for electric fuses, consisting of two insulated conducting-wires bound together and having an angular notch cut through their insulations, whereby adjacent portions of the wires are bared of insulation, and a mass of carbon wedged into said notch and4 forming a high-resistance electric bridge between the barred terminals of the wires.

Inwitness whereof I have hereunto signed my name in the'prcsenceof two subscribing witnesses.

KARL JOHN SUN DSTRM.

Witnesses:

JAMES MACBRTH, ARTHUR C. FRASER. 

